Pressure equalised rainscreen joint modelling with the numerical model PERAM

A process is developed to forecast cladding joint air pressure variations which affect rainscreen joint weathertightness in buildings, without recourse to experimental testing. A numerical model, PERAM, is presented to solve equations governing the pressure response of air within the cavity of a rainscreened joint in a building cladding when subjected to an external sinusoidal air pressure variation. A measure of the pressure equalisation performance of the joint as a percentage (the PEP) can then be calculated from the model waveforms derived, as a determination of the degree of weathertightness of the joint system. The PEPs calculated by PERAM are shown to fit the experimental data by incorporating two physically well-defined floating parameters into PERAM. This suggests that the model can be applied at the design stage of detailing weathertight pressure equalised cladding systems.